If you take care of lenses, they should last a lifetime. >=100W require a different type of glass.
The laser source has the 100k hours working before MTBF (mean time before failure).
I have 4 lenses, cost about $60 each, so I have about $240 USD in lenses. If I have a more powerful machine (>=100W) the same four lenses would be almost $2000 USD…
